When, for example, a video signal recorded in a magnetic recording medium is reproduced on a television receiver, the images reproduced may be accompanied with superimposed images such as words and dates. For the superimposed images to be produced, the video signal for superimposed images is arranged to synchronously overlap the video signal for normal picture images. That is to say that in each frame the video signal for superimposed images is overlapped on the same horizontal scanning line.
Thus, in order to overlap a video signal for superimposed images on the same horizontal scanning line, horizontal drive pulses (HD pulses) separated from a composite synchronizing signal of the reproduced video signal are sequentially counted starting from the first horizontal scanning and at the time when a predetermined number (n) of pulses has been counted the video signal for superimposed images is overlapped on the reproduction video signal. Thus, the superimposed images enter from the n'th horizontal scanning line.
When the images magnetically recorded are reproduced, the reproduced signal is unavoidably accompanied by noise signals. Thus, in the horizontal drive pulse signal which produces the HD pulses, there may occur noise such as drop-ins caused by overlapping noise pulses and drop-outs caused by dropping out of a horizontal drive pulse. Therefore, when there is a drop-out of a horizontal drive pulse in the horizontal drive pulse signal or noise pulses are overlapping on the same, the superimposed image is inserted at a horizontal scanning line which is different from the horizontal scanning line at which the superimposed image should be entered. Moreover, since this noise occurs randomly the video signal for the superimposed image overlaps a different horizontal scanning line in each of the different frames or fields forming the reproduced picture. Therefore, the superimposed images reproduced will inevitably move vertically on the screen rapidly.